If I had a toolbox in my bed, over the rails, and I wanted to get some sort of cover. Say one of those soft tonneau covers, just to keep stuff from being in plain site and exposed to the elements, could I actually get it to work with the toolbox?

I want a box but do need more store space for when traveling that is protected from the elements, but I can't get a hard tonneau and a topper is way out of my price range.